Method and apparatus for removing a pipe lining

ABSTRACT

An apparatus for removing a lining from a pipe includes a collapsible stripping tool having a plurality of extensible arms with an abrading tool mounted on each arm that is deployed by inserting the apparatus into the pipeline, supplying pressurized fluid to a cylinder to extend the arms and force the abrading tools into engagement with the lining and rotating and pulling the tool down the pipe without destroying the pipe.

TECHNICAL FIELD

The invention related to an apparatus and method for removing a lining from an underground pipe.

BACKGROUND OF THE INVENTION

Underground pipelines used to convey water, gas, sewage and other fluids have, in the past been constructed of clay tile, concrete, cast iron, ductile iron, steel or even wood. These pipelines have limited useful service lives due to deterioration of mechanical properties leading to leakage, collapse, ingress of external matter (soil), or blockages due to foreign matter buildup as a result of internal discontinuities. In some cases, deterioration of mechanical properties may be due to chemical attack. For example, concrete pipe and cast iron and/or ductile iron pipe is susceptible to interior degradation, particularly at the “crown” of the pipe, due to the effect of hydrogen sulfide gas. In other cases mechanical or environmental factors may cause the deterioration. For example, tree roots may accelerate or cause degradation or blockages of underground lines. Deterioration may occur throughout the body of the pipe or at the connections between pipe segments.

Pipe lining is a process that was developed to enhance or prolong the useful life of pipelines, in particular, underground lines. The lining is typically installed in-situ in cases wherein the mechanical and physical properties of the pipe have degraded, but before total collapse. In some cases, the lining is installed when the pipe is new during the manufacturing process with the intention of providing a barrier between the conveyed product and the host pipe material.

A number of different materials have been used in pipe lining applications. Materials originally used to form in-situ type linings included PVC (Poly Vinyl Chloride), HDPE (High Density Poly Ethylene) and CIPP (Cured In Place Pipe) materials. Additionally polyethylene lining was optionally applied to the inside surface of ductile iron pipe at the time of manufacture.

These linings provided enhanced performance and service life. However, just as the host pipes had a limited life span, typically measured in decades, so did many of the early lining systems. Many linings that slowed or stopped deterioration of the host pipes are now suffering from the same ills that plagued the original host pipes. In some cases blockages due to lining collapse have resulted where the bond between the lining and host pipe has failed or where foreign material has entered between the lining and host pipe.

Lining technology and materials have improved over time. Currently, PVC linings are only used where appropriate, HDPE linings are used in heavier walls or tighter fits than previously attempted. Poor CIPP chemistries and processes have fallen by the wayside to allow only the best CIPP methods and materials to be used. Ductile iron is no longer lined with polyethylene; rather epoxy compounds are used. These improvements will result in extended useful life for the pipelines into which the linings are installed. However in most cases, the improved methods and materials cannot be used to repair previously lined pipes without removing portions of the previously installed linings that have separated from the host pipe or otherwise degraded.

Failure of a pipe lining presents a dilemma to the owners of pipe systems that have previously been lined using early technology lining systems. In most instances, the failing lining prevents the use of new lining technologies to repair the existing host pipe, leaving the owners with two options. The lined pipe may be burst (see Streatfield et al., U.S. Pat. No. 4,738,565) and a new pipe pulled in, with some added difficulty due to the lining. Alternatively, the entire length of the pipe may be excavated to remove and replace the existing pipe. However, the host pipe holds value in that it could possibly be lined by utilizing one of the new and improved technologies.

The use of mechanical devices to clean pipes has been limited to the removal of relatively loose or soft scale and other debris from pipe lines. For example, “pigging” devices have been used in attempts to clean to steel pipelines, especially those used to transport natural gas and oil. The device is propelled through the pipe line using pressurized gas or liquid applied to one end of the pig. The pig moves axially only, brushes or scrapers mounted on the pig have one chance to remove modest amounts of scale or loose debris from the pipe. The use of a pig to clean pipe lines in this manner is typically done in a maintenance mode. Another mechanical device for cleaning pipe lines is disclosed in commonly assigned U.S. Pat. No. 6,792,820 issued Sep. 21, 2004 to Wentworth et al. The '820 patent discloses a mechanical cleaning device propelled with a rotating drill string. The device is used preparation for replacement of the buried pipe, in particular prior to bursting the host pipe and pulling in new replacement pipe. See also Harr U.S. Patent Application 20050097689, May 12, 2005, for a culvert cleaning tool and method. A need remains for a process and apparatus suitable for removing a lining or liner from an existing pipeline sufficiently to allow a new lining to be installed, as opposed to merely cleaning the inside of the pipeline leaving the existing lining in place.

SUMMARY OF THE INVENTION

A method of removing a lining from an underground pipe according to the invention includes the steps of mechanically fragmenting the lining without destroying the underground pipe, and removing the resulting lining fragments from the pipe, typically with a pressure fluid. With the lining removed, the pipe may be relined using known techniques. The existing lining will usually consist of a tubular layer of plastic bonded to the inside surface of the pipe, but with loose portions that are either unbonded from the pipe, or weakly bonded to it. For purposes of relining, it is preferred to remove these loose portions of the existing lining before covering the remnant of the old lining with a new lining.

According to another aspect of the invention, a method of removing a lining from an underground pipe includes the steps of moving a stripping tool axially through the inside of the pipe, and operating the stripping tool in a manner effective to substantially remove the lining without destroying the underground pipe. For purposes of the invention, “substantially remove the lining” means sufficient removal of loose portions so that the pipeline can be relined. The stripping tool is preferably rotated as it is moved axially through the pipe as one or more abrading tools attached to the stripper are forcibly urged in a radial direction. The abrading tool may be one or more of a stiff wire brush, serrated scraper blade, a series of knife blades mounted in a common frame, or similar devices. In one embodiment, the stripping tool includes a plurality of plurality of stripping assemblies each mounting an abrading tool and connected to a central shaft that is coaxial with the pipe, and the method includes extending the stripping assemblies in a radial direction away from the shaft and into engagement with the inside of the pipe.

In another aspect, the invention provides a collapsible rotary apparatus for removing material from the inside of a pipe. Such an apparatus includes a shaft, at least one arm mounted on the shaft, an extension and retraction mechanism connected to the arm which moves the arm in a radial direction, which mechanism includes at least one pivot about which the arm moves during extension and retraction, and an abrading tool mounted on the arm in a position for circular movement along the inside of the pipe upon rotation of the shaft. Radial extension of the arm(s) from a collapsed position to an extended position using the extension and retraction mechanism moves the abrading tool against the inside of the pipe. These and other aspects of the invention are discussed further in the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will hereafter be described with reference to the accompanying drawings, wherein like numerals denote like elements, and wherein:

FIG. 1 is a side view of a pipe lining removal apparatus according to the invention including a centering pig and a stripping tool wherein the arms of the stripping tool are illustrated in a collapsed position;

FIG. 2 is a rear view of a pipe lining removal apparatus of FIG. 1;

FIG. 3 is a side view of a pipe lining removal apparatus of FIG. 1 wherein the arms of the stripping tool are illustrated an extended or deployed position;

FIG. 4 is a rear view of a pipe lining removal apparatus of FIG. 3;

FIG. 5 is a side view of the pipe lining removal apparatus of FIG. 1 deployed in a pipeline during a lining removal operation;

FIG. 6 is a lengthwise section of the centering pig of FIG. 1:

FIG. 7 is a side view of a stripping tool according to the invention with the arms of the tool in a collapsed position;

FIG. 8 is a lengthwise section along the line 8-8 in FIG. 7;

FIG. 9 is an end view of the stripping tool of FIG. 7;

FIG. 10 is a side view of the stripping tool of FIG. 7 with the arms of the tool in an extended or deployed position;

FIG. 11 is a lengthwise section along the line 11-11 in FIG. 10;

FIG. 12 is an end view of the stripping tool of FIG. 10;

FIG. 13 is an end view of a scraping tool suitable for use in connection with a pipe line removal apparatus according to the invention;

FIG. 14 is an side view of the scraping tool of FIG. 13;

FIG. 15 is a top view of the scraping tool of FIG. 13;

FIG. 16 is a sectional view of the scraping tool of FIG. 13 taken along line 16-16 of FIG. 15;

FIG. 17 is an end view of a cutting tool suitable for use in connection with a pipe line removal apparatus according to the invention;

FIG. 18 is a side view of the cutting tool of FIG. 17;

FIG. 19 is a top view of the cutting tool of FIG. 17;

FIG. 20 is a sectional view of the cutting tool of FIG. 17 taken along line 20-20 in FIG. 19;

FIG. 21 is a rear perspective view of a stripping tool according to the invention;

FIG. 22 is an enlarged, partial view of an arm of the stripping tool of FIG. 21 illustrating the attachment of a brush tool to the arm using a bolt assembly;

FIG. 23 is a partial side view of a brush tool suitable for use in connection with a pipe line removal apparatus according to the invention;

FIG. 24 is a side view of an alternate embodiment of a pipeline stripping apparatus according to the invention;

FIG. 25 is an end view of the apparatus of FIG. 24;

FIG. 26 is a perspective view of the stripping tool shown in FIG. 24; and

FIG. 27 is a side view of the stripping tool shown in FIG. 24. Nut and bolt assemblies used to mount abrading (cutting or scraping) tools are omitted in most views.

DETAILED DESCRIPTION

Turning to FIGS. 1-5, a pipeline stripping apparatus 10 for mechanically removing a lining from an underground pipe includes a front connection or joint 12 for attaching the device to a drill string, a centering pig 14 and a second joint 16 for attaching a stripping tool 18 behind the pig. Joints 12 and 16 may be of the type disclosed in commonly owned U.S. Pat. No. 6,148,935 issued Nov. 21, 2000 to Wentworth et al. and manufactured under the trademark Splinelok® or another appropriate threaded or quick connect pipe joint. Since pig 14 serves to center stripping tool 18 in the pipeline, it is configured to fit snugly into pipe line, typically with an outside diameter ⅛″ to ½″ less than the inside diameter of the pipeline to be stripped.

Joints 12 and 16 are replaceable and, as illustrated in FIG. 6, threaded into a hollow shaft 20 that passes through a shaft tube 22 that extends axially through pig 14. An axial passage 24 extending through shaft 20 allows drilling fluid to flow from the drill string through pig 14 to stripping tool 18. Shaft 20 is mounted in bearings 26 at each end of pig 14 to allow the shaft to rotate independently of the pig. Bearing 26 are mounted in bearing flanges 28 and provided with grease seals 30 to protect the bearings from contamination as stripping apparatus 10 is pulled or pushed through a pipeline. A push plate 32 at either end of pig 14 distributes pulling or pushing forces against the flexible foam core 34 that forms the body of the pig. Pig 14 includes a slightly tapered nose 15 and is constructed by preassembling shaft tube 22, bearings and flanges 26, 28, and push plates 32 into a single unit, casting foam core 34 around the unit and then wrapping foam core 32 with a tough, durable cover 36 such as a polyurethane to protect the foam core as the pig is pulled or pushed through a pipeline.

Turning to FIGS. 1-5 and 7-12, stripping tool 18 includes a plurality of stripping assemblies 38 arranged coaxially around a central shaft or stem 44. Each of stripping assemblies 38 includes one of a leading or trailing arm 40, 42 pivotally mounted on stem 44 and a cutting, scraping, brushing or similar tool mounted on the arm. Arms 40, 42 are extensible from the position shown in FIG. 1 to the position shown in FIGS. 3 and 5. As best illustrated in FIG. 5, when extended, each of arms 40, 42 force a tool such as a scraper tool 46 or a brush tool 48 against the inside surface of a pipe 50. Pig 14 centers stripping tool 18 such that stem 44 is positioned coaxially with pipe 50.

As best shown in FIG. 5, when deployed, stripping tool 18 is pulled and rotated through pipe 50 with a drill string to mechanically abrade and remove a tubular plastic lining 52 positioned against the inside diameter of the pipe 50. In some instances, it may be desirable to remove only those sections of lining 52 that have separated from pipe 50 or have degraded. In these instances, stripping tool 18 is selectively deployed as it is pulled through pipe 50 to remove only the selected sections or portions of lining 52. With lining 52 fully or partially removed, pipe 50 may be relined with a plastic or other material using well-known techniques. In this manner, pipe 50 may be refurbished without the need for excavating the pipe or for bursting the original pipe and pulling a replacement pipe through burst original pipe.

Turning to FIGS. 7-12, arms 40, 42 each comprise a square steel channel or tube having angled forward ends 60, 62 formed by welding a short section of “C” shaped channel over the end of the tube. A tool mounting plate 64 is mounted on the rear end of each of arms 40, 42 with a slot 56 for attaching a cutting, scraping or brushing tool to the arm. As best shown in FIG. 8, plate 64 is secured to arm 40, 42 by fitting the arm into notch 58 formed in the plate and welding the arm to the plate. Each of arms 40, 42 is pivotally mounted to stem 44 with a pin 66 extending through the forward end 60, 62 of the arm and through one of arm brackets 68, 70. Arm brackets 68, 70 are welded or otherwise fastened to the circumference of stem 44 at intervals of approximately 60⁰ with brackets 70 being positioned to the rear of brackets 68 on stem 44. In this manner each of arms 40, 42 is offset radially and staggered longitudinally from the adjacent arms. The staggered configuration of arms 40, 42 allows for efficient utilization of different types of abrading tools. For example, in the configuration illustrated in FIG. 5, scraper tools 46 mounted on leading arms 40 abrade and score lining 52 before brush tools 48, which are mounted on trailing arms 42, engage the lining to brush fragments of the lining from the inside of pipe 50. As illustrated, stripping tool 18 utilizes a total of six arms 40, 42, however a greater or lesser number of arms may be employed depending upon the particular application.

Referring to FIGS. 8-11, arms 40, 42 are extended or deployed by means of a cylinder assembly 72 and links 74. Cylinder assembly 72 includes a piston 76 disposed in a central chamber 78 formed in stem 44. A piston shaft 80 extends rearwardly from piston 76 through cylinder end fixture 82 and cylinder end cap 84. A sleeve 86 including a plurality of circumferentially spaced and radially extending link brackets 88 fits over piston shaft 80 and is secured to the shaft with a shear pin 90. Links 74 extend between sleeve 86 and arms 40, 42 with the outer end of each link 74 pivotally connected to the rear end of each of arms 40, 42 by means of a link pin 92 passes through the link and through the mounting plate 64 of the arm. The inner end of each link 74 is pivotally connected to sleeve 86 by means of an arm pin 96 that passes through link brackets 88. Thus, rearward movement of sleeve 86 will cause links 74 to rotate about pins 92 and 96, extending arms 40, 42 in a radial direction.

As best illustrated in FIG. 8, a spring 98 holds piston 76 in a forward position corresponding to arms 40, 42 being in the collapsed position. To extend arms 40, 42, pressurized fluid is supplied through a fluid passage 100 to central chamber 78 to overcome the force applied to piston 76 by spring 98 and force the piston rearward, extending piston shaft 80 to the rear. As piston shaft 80 and sleeve 86 move to the rear, links 74 rotate around link pins 92 and arm pins 96 and extend outward, forcing arms 40, 42 to extend in a radial direction as illustrated in FIG. 11. As arms 40, 42 extend, scrapers 46 and brushes 48 are forced against the inside diameter of a pipeline as shown in FIG. 5. With scrapers 46 and brushes 48 held against the inside of the pipeline, apparatus 10 is rotated and pulled through the pipeline. As apparatus 10 moves through pipe 50, scrapers 46 which are mounted on leading arms 40 score and cut lining 52 while brushes 48, mounted on rear or trailing arms 42, brush fragments of the lining from the wall of the pipe.

The pressurized fluid used to actuate piston 76, typically drilling fluid or water, flows through drill string 54 (FIG. 5), axial passageway 24 in pig 14 (FIG. 6) and fluid passage 100. A plurality of fluid ports 102 (FIGS. 8 and 11) extending radially from passage 100 discharge the drilling fluid or water through metered flow nozzles 104 (FIGS. 7 and 10) in the sides of stem 44. The drilling fluid or water discharged through nozzles 104 serves to wash debris from pipe 50 as lining removing apparatus 10 is pulled through the pipe line. In one embodiment nozzles 104 are sized to discharge 14 gpm at a pressure of 500 psig which is required to fully compress spring 98. Additional pressure will increase the flow through the nozzles 104 but will not result in further extension of piston shaft 80 since the travel of piston 76 is limited by cylinder end fixture 82 when spring 98 is fully compressed.

A variety of abrading tools such as scrapers, knives, perforators and brushes may be mounted on arms 40, 42 of stripping tool 18 for removing lining 52 from a pipe line. FIGS. 14-16 illustrate a scraping tool 46 including a flexible serrated scraping blade 110 mounted in a scraping tool holder 112. Blade 110 is made from a tempered spring steel and, as illustrated, is reversible to accommodate wear. Scraping blade 110 is secured in holder 112 by fastening the blade to a cylindrical cross member 118 with bolts or screws extending through holes 114, 120 in cross member 118 and nut bar or backing rod 122, respectively As illustrated, backing rod 122 has a semi-cylindrical cross section such that blade 110 is held between the curved surfaces of cross member 118 and the backing rod so as to minimize mechanical stress on blade 110 when the blade flexes or bends during operation.

Holder 112 is welded or otherwise fastened to a mounting bracket 116 including a pair of opposed legs 124 with a section of square rod 126 welded to an inside surface of leg 124 that aids in positioning the bracket on mounting plate 64 and in retaining the bracket in position on the plate. Tool holder 112 is mounted one of arms 40, 42 by sliding mounting bracket 116 over mounting plate 64 and fastening the tool holder to the mounting plate with a bolt 130 (FIG. 22) extending through bolt hole 128 in an end flange 127 of bracket 116 and through mounting slot 56 in plate 64. In this manner, scraper tool holder 112 can be quickly and easily replaced with the removal of a single bolt.

Referring to FIGS. 17-20, a cutting tool 132 suitable for use with stripping tool 18 includes a plurality of knives 134 mounted in holes 136 in a mounting block 138. Block 138 may be constructed of an appropriate material such as nylon, another plastic or rubber material or a metal depending upon the particular design. As illustrated, holes 136 are arranged in two rows with each hole being staggered from the hole in order to increase the distance between holes as compared to a single row of holes. This configuration allows for the installation of a greater number of knives 134 in the same area.

Each of knives 134 includes a scalloped cutting end 142 and a mounting end 144 having a pin hole 146. As best illustrated in FIG. 20, knives 134 are inserted in holes 136 in mounting block 138 with pin holes 146 aligned such that a pin 148 may be inserted through block 138 and each of pin holes 146 to secure the knives in the mounting block. Mounting block 138 is attached to a mounting bracket 150 with bolts or screws 152. Mounting bracket 150, similarly to bracket 116 of FIGS. 13-16, includes a pair of opposed legs 154 with a section of square rod 156 welded to an inside surface of leg 154 and an end flange 159 with a bolt hole 158 for bolting cutting tool 132 onto an arm 40, 42 of scraping tool 18 in the same manner as described in connection with scraping tool 46 of FIGS. 13-16.

Turning to FIGS. 22 and 23, a brush tool 48 suitable for use in connection with stripping tool 18 includes two rows of “U” shaped brushes 164 mounted in holes 166 in a mounting block 168. Holes 166 are arranged in two rows with each hole staggered from the adjacent holes in the same manner as holes in the same manner as holes 136 of FIGS. 17-20. Brushes 164 are secured in holes 166 with pins 170 that extend through mounting block 168 and through the closed end of the “U” shaped brushes. Brushes 164 may be formed from a spring steel or other suitable, wear resistant material. Mounting block 168 is bolted or screwed to a mounting bracket 172 having opposed legs 174 with a section of square rod 176 welded to the inside surface of a leg 174. Rod 176 forms a pocket between the rod and opposing leg 174 to aid in mounting and retaining bracket 172 on plate 64. Brush tool 48 is attached to an arm 40, 42 of stripping tool 18 with a bolt 130 that extends through bracket 172 and through mounting slot 56 in mounting plate 64.

Referring again to FIG. 5, a method of removing lining 52 from the inside of an underground pipe 50 generally requires forming entrance and exit openings in the pipe. If existing manholes or pits do not provide the required access to pipe 50 to form the openings it may be necessary to excavate the pipe to create the openings. Once the entrance and exit opening are formed, drill string 54 is inserted into the exit opening and extended through pipe 50 to the entrance opening. Lining removal apparatus 10 is connected to the end of the drill string 54 at the entrance opening and the apparatus is inserted into pipe 50. After stripping tool 18 is completely inside pipe line 50, the drill string is rotated with the HDD and the stripping tool is deployed by supplying pressurized fluid to the tool through drill string 50. Arms 40, 42 of stripping tool 18 extend, forcibly urging scraper tool 46 and brush tool 48 against lining 52. Apparatus 10 is then pulled through the pipeline to remove lining 52. Stripping tool 18 may be selectively deployed along the length of pipe line 50 to cut, scrape and/or brush lining 52 only in those areas where the lining has separated from pipe line 50 or otherwise degraded. Lining removal apparatus 10 is then removed from pipe line 50 and the pipe line is relined using known techniques.

During the lining removal process, stripping tool 18 applies force to lining 52 in three directions. A cutting, scraping or brushing tool mounted on arms 40, 42 applies a radially directed force against the lining when arms 40, 42 are deployed. Tools mounted on arms 40, 42 also apply an axial force on lining 52 as lining removal apparatus 10 is pulled through pipe line 50. Additionally, as stripping tool 18 is rotated, tools mounted on arms 40, 42 apply a force tangential to the circumference of pipe line 50 to lining 52. In this manner, lining 52 may be cut, scraped, brushed, scored or perforated to remove loose or degraded portions of the lining and/or prepare the lining for the application of addition lining material without destroying the host pipe. Fragments of lining 52 that would tend to clog the cutting or scraping tools or otherwise interfere with the removal of lining 52 or with the re-lining operation are washed away with water or drilling fluid ejected through nozzles 104 in stripping tool 18.

One device suitable for pulling apparatus 10 through pipe 50 while rotating stripping tool 18 is a Horizontal Directional Drill (HDD) such as a D24x40 Navigator produced by Vermeer Manufacturing of Pella Iowa. While lining removal apparatus 10 is particularly suited for use with a HHD, the apparatus may be used with other machines capable of passing torque through a rod extended through a pipe, for example the HB5058 Pipe Bursting Machine manufactured and sold by Earth Tool Company LLC of Oconomowoc, Wis. Lining removal apparatus 10 may also be employed with a non-rotating drill string or rod, in which case, apparatus 10 is configured to rotate stripping tool 18 under power independently of a rod or drill string. Such rotary motion could be produced by mounting a hydraulic motor on the tool or rod and actuating it by hydraulic supply hoses towed behind the tool, thus providing the required torque to turn the tool.

FIGS. 24-27 illustrate an alternate pipeline stripping apparatus 180 according to the invention including a simplified a stripping tool 182 mounted behind a pig 14. Stripping tool 182 has a central hub 183 with radial ports 184 for the ejection of fluid received from shaft tube 22 inside pig 14. Brushes 186 similar to brushes 48 are mounted at the ends of a series of resilient steel arms 187 which extend radially from hub 183. Arms 187 act as leaf springs bent in a circumferential direction as shown. When the tool is pulled into the pipeline, arms 187 are bent inwardly, causing the brushes 186 to forcibly engage the inside of the pipeline lining 52. This arrangement is functional, but lacks the ability to deploy the arms at a desired location and retract them for ease of removal.

In a further variation, a large cylindrical brush with radially extending bristles may be employed, wherein the bristles are made of a resilient steel or similar material and are sized so that they are distorted (bent) when pulled into the pipeline, so that a radial force is exerted against the lining. This arrangement is simple and easy to make, but would lose performance as the bristle tips break off due to the constant abrasion, and the number of pipe sizes a given brush attachment could be used in would be limited. While certain embodiments of the invention have been illustrated for the purposes of this disclosure, numerous changes in the method and apparatus of the invention presented herein may be made by those skilled in the art, such changes being embodied within the scope and spirit of the present invention as defined in the appended claims. 

1. A method of removing a lining from an underground pipe, comprising: mechanically fragmenting the lining without destroying the underground pipe by removing substantially all loose portions of the lining along a length of the underground pipe; and removing resulting lining fragments from the pipe.
 2. The method of claim 1, wherein the lining comprises a tubular layer of plastic bonded to an inner peripheral surface of the underground pipe, and the loose portions comprise portions of the plastic layer weakly bonded or unbonded to the inner peripheral surface of the underground pipe.
 3. The method of claim 2, further comprising relining the underground pipe along the length of the underground pipe to be relined after the lining fragments have been removed.
 4. A method of removing a lining from an underground pipe, comprising: moving a stripping tool axially through the inside of the pipe; and operating the stripping tool in a manner effective to substantially remove the lining without destroying the underground pipe.
 5. The method of claim 4, wherein the stripping tool comprises a mechanism that rotates the stripping tool along the inside of the pipe so that the tool engages and fragments the lining.
 6. The method of claim 5, wherein the stripping tool is forcibly urged in a radial direction against the inside of the pipeline as it rotates.
 7. The method of claim 5, wherein the stripping tool is pulled through the pipeline as the stripping tool rotates.
 8. The method of claim 6, wherein the stripping tool is pulled through the pipeline as the stripping tool rotates and forcibly engages the inside of the pipeline.
 9. The method of claim 5, wherein the stripping tool comprises a stiff wire brush.
 10. The method of claim 5, wherein the stripping tool comprises a serrated scraper blade.
 11. The method of claim 5, wherein the stripping tool comprises a series of knife blades mounted in a common frame.
 12. The method of claim 4, wherein the lining comprises a tubular layer of plastic.
 13. The method of claim 6, wherein the stripping tool comprises a plurality of stripping assemblies connected to a central shaft that is coaxial with the pipe.
 14. The method of claim 13, further comprising extending the stripping assemblies in a radial direction away from the shaft and into engagement with the inside of the pipe.
 15. A collapsible rotary apparatus for removing material from the inside of a pipe, the apparatus being configured to rotate inside the pipe as the apparatus is pulled through the pipe, comprising: a shaft; at least one arm mounted on the shaft; an extension and retraction mechanism connected to the arm which moves the arm in a radial direction, which mechanism includes at least one pivot about which the arm moves during extension and retraction; and an abrading tool mounted on the arm in a position for circular movement along the inside of the pipe upon rotation of the shaft, wherein radial extension of the arm from a collapsed position to an extended position using the extension and retraction mechanism moves the abrading tool against the inside of the pipe.
 16. The apparatus of claim 15 further comprising a cylinder connected to extending the extensible arms and maintain the scraping tools in contact with the inside of the pipe under a force applied by the cylinder.
 17. The apparatus of claim 15 further comprising a plurality of extensible arms mounting abrading tools thereon coupled to the shaft at spaced intervals around the circumference of the shaft.
 18. The apparatus of claim 15 wherein the abrading tool comprises one of a brush, knife and scraper.
 19. The apparatus of claim 17 wherein at least one of the arms is axially offset from the adjacent arms. 